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Welcome to OpenCAPTCHA.org!


This site aims to define an open specification for lightweight CAPTCHA services that anyone can reuse across multiple World Wide Web sites. These services may or may not use the well-known and well-established "warped text image" technique, but might provide other innovative CAPTCHA techniques as well, including perhaps:

• Identify an item in a grid of similar looking items
• Trivia questions
• Quickie two-second Flash games
• Grammatical questions
• etc.

The aim is to make CAPTCHA as quick and easy to implement as possible, while at the same time providing a continuously evolving repository of CAPTCHA algorithms that adapt to the impositions of web spam.

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The OpenCAPTCHA.org Specification

The current version of the spec is the early v0.1.1 rough draft.

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Sample Implementations

new movies download Sample Challenge Answer Service (ASP.NET MVC source)

Sample Challenge Service (ASP.NET MVC source)

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Complete samples:

ASP.NET MVC

http://opencaptcha.org/sample/0.1/website/

Challenge-Answer Provider service: http://opencaptcha.org/sample/0.1/challenge-answer/challengeanswer/
Challenge sevice: http://opencaptcha.org/sample/0.1/challenge/challenge/

Source code: OpenCAPTCHA.org v0.1 ASP.NET MVC Sample.zip